Chapter 27: Fluid, Electrolyte and Acid-base Balance BIO 211 Lecture Instructor: Dr. Gollwitzer 1.
Chapter 29: Development BIO 211 Lecture Instructor: Dr. Gollwitzer 1.
-
Upload
gervase-caldwell -
Category
Documents
-
view
227 -
download
1
Transcript of Chapter 29: Development BIO 211 Lecture Instructor: Dr. Gollwitzer 1.
• Today in class we will:– Define and describe development– Trace the general processes from ovulation through
fertilization and formation of a zygote– List the stages of development– List the 3 stages of gestation and briefly describe the
major events associated with each• Distinguish between embryo and fetus• Discuss the two major roles of the placenta• Discuss the basic structural and functional changes in the uterus
during gestation– Briefly describe the events that occur during labor and
delivery– Describe lactation and milk let-down reflex
2
Development
• Begins with fertilization (conception) =– When male and female gametes (sperm and
egg) unite to form single-cell zygote– Occurs in uterine tube 12-24 hr after ovulation
• Is the gradual modification from fertilization to maturity of:– Anatomical structures– Physiological characteristics
3
Amphimixis
• Fusion of female and male pronuclei• Moment of conception• Cell becomes zygote (46 chromosomes)• Fertilization complete
5
Stages of Development
• Prenatal – before birth– Embryological development• Occurs during first 2 mo after fertilization• Organs established
– Fetal development• Begins at 9th wk and continues to birth• Organs develop
• Postnatal – after birth– Neonate = newborn
6
Gestation
• Time spent in prenatal development• Consists of 3 trimesters, each 3 months long– First trimester– Second trimester– Third trimester
7
First Trimester• Cell cleavage (division) and blastocyst formation• Blastocyst implantation = burrowing into uterine
wall• Placentation = formation of placenta– Temporary structure in uterine wall – Permits diffusion between fetal and maternal
circulatory systems• Embryogenesis – all organ systems begin to be
established; but nonfunctional– Embryo = organism in the developmental stage
beginning at fertilization and ending at the start of the third developmental month (weeks 1 – 8)
8
First Trimester
• Most dangerous period in prenatal life• Only 40% of conceptions produce embryos
that survive past first trimester
9
Placenta
• Complex organ that permits exchange between maternal and embryonic circulatory systems
• Supports fetus in second and third trimesters
• Stops functioning and is ejected from uterus after birth
12
First Trimester: hCG
• hCG = human chorionic gonadotropin• Produced by placenta• Appears in maternal bloodstream soon after
implantation• Used as pregnancy test/kit• Maintains CL for 3-4 months– So CL P (until placenta takes over P production)
18
Second Trimester
• Fetal stage = development of all organ systems (organogenesis)
• Rapid growth of fetus– Fetus = organism in the developmental stage
lasting from the start of the third developmental month to delivery (week 9 through delivery)
• Body proportions change• Progesterone levels increase
19
Third Trimester Hormones• P (placental)– Until 3rd trimester, “calms” myometrium so no
contractions
• E (placental)– Increases myometrial contractions– Sensitizes uterus to oxytocin (maternal and fetal)
prostaglandins (PGs) initiate labor
27
Third Trimester Hormones• Human placental lactogen (hPL)– Helps prepare mammary glands for milk
production– Effects on other tissues comparable to GH
• Prolactin (placental)– Helps convert mammary glands to active status
• Relaxin (CL and placental) – Increased flexibility of pubic symphysis pelvis
expands– Dilation of uterine cervix so fetus can enter
vagina
28
Labor• False– Occasional spasms in uterine musculature– Contractions not regular or persistent
• True– Results from biochemical and mechanical factors– Continues due to positive feedback
• Premature– When labor begins before fetal development
complete; survival related to BW
30
Labor and Delivery
• Goal: parturition = forcible expulsion of fetus• Stages of labor– Dilation– Explusion– Placental
31
Labor and Delivery
• Dilation stage– Begins with onset of true labor– Cervix dilates– Fetus moves toward cervical canal– Frequency of contractions increases– Amniochorionic membrane ruptures (“water
breaks”)
32
Labor and Delivery
• Expulsion stage– Cervix completely dilated– Maximum intensity of contractions– Continues until fetus emerges from vagina =
delivery/birth
34
Labor and Delivery
• Placental stage– Uterine contractions tear connection between
endometrium and placenta– Placenta (afterbirth) ejected– Accompanied by loss of blood, usually tolerated
without difficulty
35